The human immune system has a myriad of diverse T-cell clones, each contributing to the effective and optimal immune responses towards foreign- or self-antigens. If proper control of the “anti-self” immune response is not imposed and maintained, the resulted “anti-self” response leads to development of autoimmune diseases. While the vast majority of self-reactive T-cell clones is deleted in the thymus (negative selection), some remain self-responsive, thus creating self-attacking T effector cells. To counterbalance these problems, there is a specialized population of T-cells called regulatory T-cells (Tregs) able to suppress the activation and expansion of other T-cells to maintain a fine homeostatic balance between reactivity to foreign- and self-antigens. These Tregs are characterized by a high level expression of surface interleukin-2 receptor a chain (CD25) and an intracellular expression of a master switch transcription factor called forkhead box protein P3 (Foxp3). There are at least two important functional populations of Tregs, namely natural Tregs (nTregs) that are continuously derived from the thymus and induced Tregs (iTregs) that are converted from peripheral naive CD4+ T-cells. Transforming growth factor-β (TGF-) modulates the expansion of nTregs and induces conversion of CD4+CD25− naïve T cells into CD4+CD25+ iTregs both in vitro and in vivo. While TGF-β-induced conversion to iTregs was explored for the application as future therapy for autoimmune diseases, the method proved to be unreliable and producing unstable iTregs, easily losing both Foxp3 expression and suppressor function upon environmental change (no exogenous TGF-β) and after repeated re-stimulation.
In spite of considerable research into this technology, the previous solutions have proven unreliable. The present invention provides stable Tregs and related methods and compositions.
The T-cell receptor (TCR) that is made up of TCRα and TCRβ chains has an exquisite specificity for its peptide antigen presented by the major histocompatibility complex (MHC) expressed on antigen presenting cells (APCs). Engagement of the TCR by peptide/MHC ligand controls T-cell generation and function. In transplantation, an acute rejection is mainly mediated by direct recognition of donor allo-MHC on “passenger APCs,” while chronic rejection by the processed allopeptides presented by host self-MHC. Great efforts have been devoted to study the peptide-MHC/TCR interaction (1) and associated fates of T-cells during clonal expansion followed by clonal contraction (2-4). Moreover, manipulation of TCR engagement by modification of peptide/antigen or TCR engineering have been explored for potential therapeutic applications (5-7).
Binding of surface receptors by monoclonal antibodies (mAbs) may result in the depletion of cells or in the agonistic/antagonistic effects mimicking/blocking the action of the receptor's natural ligands (8). The inventors have explored the therapeutic potential of a TCRβ chain-specific mAb (9). This is different from the first mAb approved for clinical application namely mouse anti-human CD3 agonist (OKT3 mAb). The OKT3 mAb targets the ε chain within the CD3εγ or εδ dimers, which is implicated in the signaling of the TCR/CD3 complex (10;11). Initially, the OKT3 mAb was used as an effective agent to prevent the post-transplant acute rejection. Nevertheless, OKT3 mAb was shown to be a potent mitogenic agent for T-cells; almost immediately after administration, OKT3 mAb elicited the release of many cytokines causing flu-like symptoms in treated patients (12). To reduce such side effects, the FcR-non-binding humanized anti-CD3 mAbs (teplizumab) was developed (13). Because the Protégé Encore phase III clinical study with teplizumab was suspended for the lack of sufficient efficacy for type 1 diabetes (T1D) and other clinical trials with anti-CD3 mAb are still underway (14), its long-term therapeutic effects remain obscure. Thus, safer and more effective methods to modulate the TCR signal are still needed for induction of tolerance.
In 1994, the inventors applied a mouse anti-human TCR mAb (clone BMA 031) as an induction therapy for kidney transplant patients. Transient administration of BMA 031 mAb improved kidney allograft survival, and none of the treated patients showed even moderately adverse effects as seen in OKT3 mAb-treated patients (15). Later, another group also showed that a different anti-human TCR mAb (clone T10B9) provided treatment for allograft rejection as effective as that of OKT3 mAb with fewer untoward effects, namely less cytokine release and fewer serious infections (16). The inventors and other groups confirmed the effectiveness of anti-TCR mAbs in preventing skin allograft rejection (17), graft-versus-host disease (18), and in the synergistic interaction with cyclosporine to prolong rat heart allograft survivals (9). Recent clinical reports re-emphasized the importance of using antibodies for induction therapies not only to prevent initial acute rejection but also to promote long-term allograft survival (19). The aim of this study was to determine whether TCR-specific mAb has robust tolerogenic effects in models of organ allograft transplantation and for treating T1D. The inventors found that transient anti-TCRβ mAb therapy (clone H57-597) led to: 1) initial reduction of conventional T-cells number with enrichment of FoxP3-expressing Treg cells; 2) minimal cytokine production; 3) abrogation of antigen-specific T-cell responses; 4) protection against the onset of T1D; 5) remission of new onset T1D; and 6) induction of tolerogenic effects to heart allografts. The inventors' findings revealed that transient TCR modulation by anti-TCR mAb provides a potent therapeutic approach for induction of tolerance in T1D and in organ transplant models.
There is no admission that the background references disclosed in this section legally constitutes prior art.